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Ward's World Hydrophobic Effect Activity

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Page 1 Fear of Water Recommended Grade Level(s): Appropriate for: Middle school and High school Time Requirements: Activity Time: 20 minutes Teaching Topics & Concepts: • Hydrogen bonding, hydrophobic bonding, surface tension • Properties of water molecules • Observation skills Background: This activity is no day at the beach. Normal beach sand is polar, which makes it hydrophilic (water-loving). When regular beach sand comes in contact with water, the water's polarity causes it to stick the sand together. That's how we can build those incredible sandcastles. When individual grains of sand are treated with a hydrophobic monolayer, it becomes hydrophobic sand. This process creates a non-polar (hydrophobic) layer on the surface of the sand grain. The hydrophobic layer repels water from the surfaces of individual grains of sand. Now instead of causing the grains of sand to stick together, water either repels or completely envelops the non-polar sand, so it bonds with itself. It never gets wet, so students can build their sandcastles, coral reefs (or other works of art) under water! Materials: • Hydrophobic sand • Ethanol • Water • Filter paper • Funnel • (2) 400 mL beakers Procedure: 1. Pour 200 mL of water into a 400 mL beaker. 2. Sprinkle some hydrophobic sand onto the water. 3. Try to push the sand down with your finger. 4. Sprinkle more sand into the beaker so that some falls to the bottom. 5. Pour 200 mL of ethanol into a second 400 mL beaker. 6. Sprinkle hydrophobic sand into this second beaker and observe. + ward ' s science Safety • Read the SDS sheet for ethanol. • Wear safety glasses and gloves. • Alcohol is highly volatile and flammable. Ensure no open flames are present (candle, Bunsen burner). • Avoid inhalation of alcohol vapors. !

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